Lee attacked with about 57,000 men against 34,000 Union soldiers.

Both sides paid heavily, the Union losing about 6,800 and the Confederates nearly 9,000.

This was the third of the Seven Days’ Battles. On June 27, 1862, Gen. Robert E. Lee renewed his attacks against Porter’s strongly reinforced V Corps, which had established a strong defensive line behind Boatswain’s Swamp north of the Chickahominy River. But Lee knew that however strong the Union position tactically, it was strategically isolated on the north side of the Chickahominy swamps, with few bridges for reserves or retreat. Naturally aggressive, and already committed to his operation, Lee continued the attack.

Porter’s men held fast for five hours of the afternoon against disjointed Confederate attacks, inflicting heavy casualties. At dusk, the Confederates finally mounted a coordinated assault that broke Porter’s line and drove his soldiers back toward the river. John Bell Hood’s Texans (and Evander Law’s Alabamians) showed their guts by charging straight through the Union position and only firing once they had broken the line. (Previous attacks had all lost momentum when the soldiers paused to fire back at the defenders, and in the ensuing firefights the defenders had all the advantages.) The weight and speed of the three brigade charge (George Pickett’s Virginians were in support) sent the Union line reeling and many prisoners were taken.

McClellan had to order a withdrawal across the Chickahominy – and that also meant he had to give up his base at White House, switching from the York to the James. And with McClellan rattled, it was almost guaranteed that he would fall back toward that base. Lee had got what he wanted: McClellan’s pressure on Richmond was over, and it remained to see if Lee could trap the Army of the Potomac.